1. Field of the Invention
This invention relates to a method of making a breathable film laminate, more particularly to a method of making a breathable film laminate including a breathable TPU film.
2. Description of the Related Art
A conventional breathable film made of thermoplastic polyurethane (TPU) that is hydrophilic and that has liquid-impermeable and vapor-permeable properties, generally encounters a problem of swelling upon contact with water. Thus, when the thickness of the thermoplastic polyurethane film is small, the film is likely to form wrinkles which are undesirable for the appearance of the film. When the thickness of the thermoplastic polyurethane film is increased, although the wrinkle problem can be alleviated, the vapor-permeability of TPU will be reduced.
An improvement over the TPU breathable film provides a laminate that includes a thermoplastic polyurethane film having two opposite sides bonded to two fabric layers through an adhesive, thereby reducing the wrinkle problem of the thermoplastic polyurethane film. However, liquid impermeability and vapor permeability become low due to the use of the adhesive, and the cost of materials increases due to the use of the fabric layers.